CMOS inputs are very high impedance, they include an NMOS and PMOS totem pole inverting buffer. When defined (V_I = V_CC or GND) either the PMOS or the NMOS is off. There is no current path from V_CC to ground. Unused inputs must be terminated to prevent the input circuitry from floating into the linear mode of operation. In the linear mode of operation, neither the PMOS nor the NMOS is switched off. A crossbar current, ΔI_CC flows from V_CC to ground. Extra power dissipation, false switching and oscillation can all result from inputs floating into the linear mode of operation. In cases where the driver of the input may be disabled, external resistors are used to prevent the input from floating. These resistors pull the input up to V_CC or down to ground.